Method of forming bandgap reference integrated circuit

ABSTRACT

A method of forming an integrated circuit comprises forming a first doped region and a second doped region in a substrate. The second doped region is formed separate from the first doped region by a first spacing. A dielectric layer is formed over the substrate, and a gate is formed over the dielectric layer. The gate is positioned having the first doped region on a first substrate side of the gate and the second doped region on a second substrate side of the gate, opposite the first substrate side of the gate. A third doped region is formed in the substrate separated from the first doped region by a second spacing. The method further comprises forming a fourth doped region in the substrate.

PRIORITY CLAIM

The present application is a divisional of U.S. application Ser. No. 14/458,994, filed Aug. 13, 2014, which is incorporated herein by reference in its entirety.

BACKGROUND

Some voltage reference circuits, such as bandgap reference circuits, operate at very low voltages and currents. Some reference circuits include complementary metal-oxide-semiconductor (CMOS) transistors that have gates through which a current flows. The low voltages and currents require the CMOS transistors to have high resistance in order to satisfy Ohm's Law (i.e., V=IR). For example, if a reference circuit has a base emitter voltage of 30 millivolts (mV) and a current of 3 nano Amps (nA) that flow through a gate of a CMOS transistor, to satisfy Ohm's law the CMOS transistor has a resistance of 10 mega Ohms (MΩ).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a diagram of an integrated circuit, in accordance with one or more embodiments.

FIG. 2 is a flowchart of a method of forming an integrated circuit, in accordance with one or more embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

To satisfy Ohm's law, a complementary metal-oxide-semiconductor (CMOS) reference circuit that operates at very low voltages and currents, such as 30 mV and 3 nA, must have a poly resistance in the CMOS transistor of 10 MΩ. Some CMOS technologies have a gate poly resistance of about 500 Ω per unit square area of gate material. To achieve 10 MΩ of resistance, the example CMOS transistor would require a quantity of 20,000 squares of poly gate material resulting in total greater than 300 μm² area.

As demand for low power consumption and decreased device size increases, a CMOS reference circuit that requires 20,000 squares of poly gate material to achieve 10 MΩ of resistance requires too large of an area for many applications. Further, to form a CMOS transistor that has more than a 500 Ω resistance per square with a cross-sectional area of 300 μm² of poly gate material, the manufacturing process uses multiple masking steps, which reduces production efficiency and increases manufacturing costs.

FIG. 1 is a diagram of an integrated circuit 100 according to an embodiment. Integrated circuit 100 is a bandgap reference circuit having a resistance level ranging from 1 MΩ˜10 MΩ at low voltages and currents. Compared to other CMOS reference circuits that would normally require 20,000 squares of poly gate material to achieve 1 MΩ˜10 MΩ resistance levels, integrated circuit 100 is more than 60% smaller in area, while still achieving at least 1 MΩ˜10 MΩ resistance levels.

Integrated circuit 100 comprises a substrate 101 having a well region 103, and a first doped region 105 a in the well region 103. Well region 103 also has a second doped region 105 b. The second doped region 105 b is horizontally separated from the first doped region 105 a by a first spacing S1. In some embodiments, the spacing S1 is a distance that ranges from about 10 nm to about 1 um. Further, well region 103 also has a third doped region 105 c. The third doped region 105 c is horizontally separated from the first doped region 105 a by a second spacing S2. In some embodiments, the spacing S2 is a distance that ranges from about 50 nm to about 1 um. A fourth doped region 107 is in the well region 103. A dielectric layer 109 is over the substrate 101. The dielectric layer 109 is over the substrate 101 and contacts a surface 111 of the substrate 101 extending between the first doped region 105 a and the second doped region 105 b. In some embodiments the dielectric layer 109 has a thickness that ranges from about 0.1 nA to about 10 nm.

A gate layer 113 is over the dielectric layer 109. The gate layer 113 is positioned having the first doped region 105 a in the substrate 101 on a first substrate side 113 a of the gate layer 113, and the second doped region 105 b is in the substrate 101 on a second substrate side 113 b of the gate layer 113 opposite the first substrate side 113 a of the gate layer 113. The gate layer 113 is coupled with a first input 115 of an operational amplifier 117. The third doped region 105 c is coupled with a second input 119 of the operational amplifier 117. The gate layer 113 and an output 121 of the operational amplifier 117 are coupled with a first transistor 123. The third doped region 105 c and the output 121 of the operational amplifier 117 are coupled with a second transistor 125. The first transistor 123 and the second transistor 125 are coupled with a first voltage supply Vdd. The fourth doped region 107 is coupled with a second voltage supply Vss. The gate layer 113, the operational amplifier 117, and the third doped region 105 c are coupled with the first voltage supply Vdd by way of the first transistor 123 and the second transistor 125. The first voltage supply Vdd, for example, is a drain voltage and the second voltage Vss is a source voltage.

Substrate 101 comprises a semiconductor material such as a silicon, a silicon-on-insulator, or other suitable material. The dielectric layer 109 is an oxide or other suitable material. The gate layer 113 comprises a polymer material, a polysilicon material, or other suitable material.

The first doped region 105 a, the second doped region 105 b, and the third doped region 105 c have a first doping type. The fourth doped region 107 has a second doping type different from the first doping type. In some embodiments, the first doping type is p-type and the second doping type is n-type. In other embodiments, the first doping type is n-type and the second doping type is p-type. The well region 103 has the second doping type. The first doped region 105 a, the second doped region 105 b and the third doped region 105 c are, for example, source/drain regions.

In some embodiments, the first doped region 105 a is optionally coupled with the second doped region 105 b by an optional fifth doped region 127. The fifth doped region 127 has the first doping type. The first doped region 105 a, the second doped region 105 b, and/or the third doped region 105 c have a first doping concentration. The optional fifth doped region 127 has a second doping concentration different from the first doping concentration. In some embodiments, the optional fifth doped region 127 has the first doping concentration. For example, if the first doping type is p-type, the first doping concentration is P+, meaning that a region having a doping concentration of P+ is a more heavily doped region compared to a region having a standard p-type doping. The fourth doped region 107 has a doping concentration greater than a doping concentration of the well region 103. For example, if the second doping type is n-type, the fourth doped region 107 has an N+ doping concentration while the well region has a standard n-type doping.

The gate layer 113 has a width W1 in a horizontal direction. The width W1 of the gate layer 113 is equal to the first spacing S1. In some embodiments, the width W1 is greater than the first spacing S1. In other embodiments, the width W1 is less than the first spacing S1. The dielectric layer 109 has a width W2 in a horizontal direction. The width W2 of the dielectric layer 109 is equal to the width W1 of the gate layer 113. In some embodiments, the width W2 of the dielectric layer 109 is less than the width W1 of the gate layer 113. In some embodiments, the width W2 of the dielectric layer 109 is greater than the width W1 of the gate layer 113. In some embodiments, the width W2 of the dielectric layer 109 is equal to the first spacing S1. In some embodiments, the width W2 of the dielectric layer 109 is greater than the first spacing S1. In some embodiments, the width W2 of the dielectric layer 109 is less than the first spacing S1.

The first doped region 105 a extends from the surface 111 of the substrate 101 to a first depth D1 from the surface 111 of the substrate 101. The second doped region 105 b extends from the surface 111 of the substrate 101 to a second depth D2 from the surface 111 of the substrate 101. The first depth D1 is equal to the second depth D2. In some embodiments, the first depth D1 is greater than or less than the second depth D2. The optional fifth doped region 127 extends from the surface 111 of the substrate 101 to a third depth D3 from the surface 111 of the substrate 101. The third depth D3 is different from the first depth D1 and the second depth D2. In some embodiments, the third depth D3 is less than the first depth D1 and the second depth D2.

In some embodiments, by including the dielectric layer 109, fewer masks are used when manufacturing the integrated circuit 100 as compared to a reference circuit that would attempt to achieve a 10 MΩ resistance without having a gate dielectric or oxide layer such as dielectric layer 109. Because integrated circuit 100 includes the dielectric layer 109, integrated circuit 100 has the capability of consuming less than 10 nano Watts (nW) of power when in use.

FIG. 2 is a flowchart of a method 200 of forming an integrated circuit, in accordance with one or more embodiments.

In step 201, a well region such as well region 103 (FIG. 1) is formed in a substrate such as substrate 101 (FIG. 1) by, for example, an ion implantation process or other suitable process.

In step 203, a first doped region such as first doped region 105 a (FIG. 1), a second doped region such as second doped region 105 b (FIG. 1) and a third doped region such as third doped region 105 c (FIG. 1) are formed in the substrate by, for example, an ion implantation process or other suitable process by, for example, one or more ion implantation processes or other suitable processes. The first doped region and the second doped region are separated by a first spacing, e.g., spacing S1. The first doped region and the third doped region are separated by a second spacing, e.g., spacing S2.

In step 205, a fourth doped region such as fourth doped region 107 (FIG. 1) is formed in the substrate by, for example, an ion implantation process or other suitable process.

In step 207, an optional fifth doped region such as fifth doped region 127 (FIG. 1) is formed in the substrate using an implantation process or other suitable process. The fifth doped region is formed coupling the first doped region with the second doped region.

In step 209, a dielectric layer such as dielectric layer 109 (FIG. 1) is formed over the substrate using physical vapor deposition (PVD), chemical vapor deposition (CVD), epitaxial growth, or other suitable process. In some embodiments, the dielectric layer is deposited or grown over the substrate and etched to have a predetermined width and/or position over the substrate. In other embodiments, the dielectric layer is deposited or grown in a predetermined position having a predetermined width over the substrate.

In step 211, a gate such as gate layer 113 (FIG. 1) is formed over the dielectric layer using low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), or other suitable process.. The gate is formed having the first doped region in the substrate positioned on a first substrate side of the gate, and the second doped region in the substrate positioned on a second substrate side of the gate opposite the first substrate side of the gate.

In step 213, the gate and the third doped region are coupled with an operational amplifier such as operational amplifier 117 (FIG. 1) by one or more conductive lines.

In step 215, the gate, the third doped region and the operational amplifier are coupled with a first transistor and a second transistor such as first transistor 123 (FIG. 1) and second transistor 125 (FIG. 1) by one or more conductive lines.

In step 217, the first transistor and the second transistor are coupled with a first voltage supply such as first voltage supply Vdd (FIG. 1) by one or more conductive lines, thereby coupling the gate, the third doped region and the operation amplifier with the first voltage supply.

In step 219, the fourth doped region is coupled with a second voltage supply different from the first voltage supply such as second voltage supply Vss (FIG. 1) by one or more conductive lines.

In an embodiment, a method of forming an integrated circuit includes forming a first doped region of a first doping type in a substrate; forming a second doped region of the first doping type in the substrate, the second doped region being formed with a first spacing separating the first doped region from the second doped region; forming a dielectric layer over the substrate; forming a gate over the dielectric layer, the gate being formed having the first doped region in the substrate positioned on a first substrate side of the gate, and the gate being formed having the second doped region in the substrate positioned on a second substrate side of the gate opposite the first substrate side of the gate; forming a third doped region of the first doping type in the substrate, the third doped region being formed with a second spacing separating the first doped region from the third doped region; forming the first, second, and third doped regions includes forming the first, second, and third doped regions in a well region of a second doping type, different from the first doping type; connecting the gate with a first node by a first conductive line, wherein the first node is configured to be coupled to a first voltage supply; connecting the third doped region with a second node by a second conductive line, wherein the second node is configured to be coupled to the first voltage supply; and connecting the well region with a third node by a third conductive line, wherein the third node is configured to be coupled to a second voltage supply. In an embodiment, the first and second conductive lines are configured to be connected to an operational amplifier. In an embodiment, the method includes forming a fourth doped region of the first doping type in the well region using an implantation process, the fourth doped region being formed coupling the first doped region with the second doped region. In an embodiment, forming the first doped region, the second doped region, and the fourth doped region includes forming the first doped region to extend from a surface of the substrate to a first depth from the surface of the substrate, forming the second doped region to extend from the surface of the substrate to a second depth from the surface of the substrate, and forming the fourth doped region to extend from the surface of the substrate to a third depth from the surface of the substrate, the third depth being different from the first depth and the second depth. In an embodiment, the first doped region and the second doped region are formed having a first doping concentration, and the fourth doped region is formed having a second doping concentration different from the first doping concentration. In an embodiment, the first conductive line is configured to be coupled to a first transistor, and the second conductive line is configured to be coupled to a second transistor. In an embodiment, the gate is formed to have a width equal to the first spacing. In an embodiment, the dielectric layer is formed to have a width equal to the width of the gate. In an embodiment, the dielectric layer is formed to have a width equal to the first spacing. In an embodiment, the method includes forming a fifth doped region of the second doping type in the well region, and connecting the fifth doped region to the second voltage supply. In an embodiment, the method includes forming the fifth doped region to have a doping concentration greater than a doping concentration of the well region.

In an embodiment, a method of forming an integrated circuit includes forming a well region in a substrate; forming a first doped region in the well region; forming a second doped region in the well region, the second doped region being formed spaced from the first doped region by a first spacing separating the second doped region from the first doped region; forming a dielectric layer over the well region and contacting a surface of the substrate extending between the first doped region and the second doped region; forming a gate over the dielectric layer; forming a third doped region in the well region, the third doped region being formed spaced from the first doped region by a second spacing separating the third doped region from the first doped region; connecting the gate with a first node by a first conductive line, wherein the first node is configured to be coupled to a first voltage supply; connecting the third doped region with a second node by a second conductive line, wherein the second node is configured to be coupled to the first voltage supply; connecting the well region with a third node by a third conductive line, wherein the third node is configured to be coupled to a second voltage supply; forming the first doped region, the second doped region, and the third doped region to have a same first doping type; and forming the well region to have a second doping type different from the first doping type. In an embodiment, the method includes forming an implant region under the dielectric layer, wherein the implant region connects the first doped region and the second doped region. In an embodiment, forming the first doped region, the second doped region, and the implant region includes forming the first doped region to extend from a surface of the substrate to a first depth from the surface of the substrate, forming the second doped region to extend from the surface of the substrate to a second depth from the surface of the substrate, and forming the implant region to extend from the surface of the substrate to a third depth from the surface of the substrate, the third depth being different from the first depth and the second depth. In an embodiment, forming the first doped region, the second doped region, and the implant region includes forming the first doped region and the second doped region to have a first doping concentration, and the implant region is formed to have a second doping concentration different from the first doping concentration. In an embodiment, the first conductive line and the second conductive line are configured to be connected to an operational amplifier, the first conductive line is configured to be connected to a first transistor, and the second conductive line is configured to be connected to a second transistor. In an embodiment the dielectric layer is formed to have a width equal to the width of the gate.

In an embodiment, a method of forming a bandgap reference circuit includes forming a first p-doped region in a substrate; forming a second p-doped region in the substrate, the second p-doped region being formed spaced from the first p-doped region by a first spacing separating the second p-doped region from the first p-doped region; forming a dielectric layer over the substrate; forming a gate over the dielectric layer, the gate being formed having the first p-doped region in the substrate on a first substrate side of the gate, and the gate positioned having the second p-doped region in the substrate on a second substrate side of the gate, opposite the first substrate side of the gate; forming a third p-doped region in the substrate, the third p-doped region being formed spaced from the first p-doped region by a second spacing; forming an n-doped region in the substrate; connecting the gate with a first node by a first conductive line, wherein the first node is configured to be coupled to a first voltage supply; connecting the third p-doped region with a second node by a second conductive line, wherein the second node is configured to be coupled to the first voltage supply; connecting the n-doped region with a third node by a third conductive line, wherein the third node is configured to be coupled to a second voltage supply; and forming the first p-doped doped region, the second p-doped doped region, the third p-doped doped region, and the n-doped region within a common, n-doped well region. In an embodiment, the gate is formed to have a width equal to the first spacing, and the dielectric layer is formed to have a width equal to the width of the gate. In an embodiment, the method includes forming a p-doped implant region in the substrate to connect the first p-doped region and the second p-doped region.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method of forming an integrated circuit, the method comprising: forming a first doped region of a first doping type in a substrate; forming a second doped region of the first doping type in the substrate, the second doped region being formed with a first spacing separating the first doped region from the second doped region; forming a dielectric layer over the substrate; forming a gate over the dielectric layer, the gate being formed having the first doped region in the substrate positioned on a first substrate side of the gate, and the gate being formed having the second doped region in the substrate positioned on a second substrate side of the gate opposite the first substrate side of the gate; forming a third doped region of the first doping type in the substrate, the third doped region being formed with a second spacing separating the first doped region from the third doped region, wherein forming the first, second, and third doped regions comprises forming the first, second, and third doped regions in a well region of a second doping type, different from the first doping type; connecting the gate with a first node by a first conductive line, wherein the first node is configured to be coupled to a first voltage supply; connecting the third doped region with a second node by a second conductive line, wherein the second node is configured to be coupled to the first voltage supply; and connecting the well region with a third node by a third conductive line, wherein the third node is configured to be coupled to a second voltage supply.
 2. The method of claim 1, wherein the first and second conductive lines are configured to be connected to an operational amplifier.
 3. The method of claim 1, further comprising: forming a fourth doped region of the first doping type in the well region using an implantation process, the fourth doped region being formed coupling the first doped region with the second doped region.
 4. The method of claim 3, wherein forming the first doped region, the second doped region, and the fourth doped region comprises: forming the first doped region to extend from a surface of the substrate to a first depth from the surface of the substrate; forming the second doped region to extend from the surface of the substrate to a second depth from the surface of the substrate; and forming the fourth doped region to extend from the surface of the substrate to a third depth from the surface of the substrate, the third depth being different from the first depth and the second depth.
 5. The method of claim 3, wherein the first doped region and the second doped region are formed having a first doping concentration, and the fourth doped region is formed having a second doping concentration different from the first doping concentration.
 6. The method of claim 1, wherein the first conductive line is configured to be coupled to a first transistor, and the second conductive line is configured to be coupled to a second transistor.
 7. The method of claim 1, wherein the gate is formed to have a width equal to the first spacing.
 8. The method of claim 7, wherein the dielectric layer is formed to have a width equal to the width of the gate.
 9. The method of claim 1, wherein the dielectric layer is formed to have a width equal to the first spacing.
 10. The method of claim 1, further comprising: forming a fifth doped region of the second doping type in the well region; and connecting the fifth doped region with the third node by the third conductive line.
 11. The method of claim 10, further comprising: forming the fifth doped region to have a doping concentration greater than a doping concentration of the well region.
 12. A method of forming an integrated circuit, the method comprising: forming a well region in a substrate; forming a first doped region in the well region; forming a second doped region in the well region, the second doped region being formed spaced from the first doped region by a first spacing separating the second doped region from the first doped region; forming a dielectric layer over the well region and contacting a surface of the substrate extending between the first doped region and the second doped region; forming a gate over the dielectric layer; forming a third doped region in the well region, the third doped region being formed spaced from the first doped region by a second spacing separating the third doped region from the first doped region; connecting the gate with a first node by a first conductive line, wherein the first node is configured to be coupled to a first voltage supply; connecting the third doped region with a second node by a second conductive line, wherein the second node is configured to be coupled to the first voltage supply; and connecting the well region with a third node by a third conductive line, wherein the third node is configured to be coupled to a second voltage supply, wherein the first doped region, the second doped region, and the third doped region are formed having a same first doping type, and the well region is formed having a second doping type different from the first doping type.
 13. The method of claim 12, further comprising: forming an implant region under the dielectric layer, wherein the implant region is formed connecting the first doped region and the second doped region.
 14. The method of claim 13, wherein forming the first doped region, the second doped region, and the implant region comprises: forming the first doped region to extend from a surface of the substrate to a first depth from the surface of the substrate; forming the second doped region to extend from the surface of the substrate to a second depth from the surface of the substrate; and forming the implant region to extend from the surface of the substrate to a third depth from the surface of the substrate, the third depth being different from the first depth and the second depth.
 15. The method of claim 13, wherein forming the first doped region, the second doped region, and the implant region comprises: forming the first doped region and the second doped region to have a first doping concentration, and forming the implant region to have a second doping concentration different from the first doping concentration.
 16. The method of claim 12, wherein the first conductive line and the second conductive line are configured to be connected to an operational amplifier, the first conductive line is configured to be connected to a first transistor, and the second conductive line is configured to be connected to a second transistor.
 17. The method of claim 12, wherein the dielectric layer is formed to have a width equal to the width of the gate.
 18. A method of forming a bandgap reference circuit, the method comprising: forming a first p-doped region in a substrate; forming a second p-doped region in the substrate, the second p-doped region being formed spaced from the first p-doped region by a first spacing separating the second p-doped region from the first p-doped region; forming a dielectric layer over the substrate; forming a gate over the dielectric layer, the gate being formed having the first p-doped region in the substrate on a first substrate side of the gate, and the gate positioned having the second p-doped region in the substrate on a second substrate side of the gate, opposite the first substrate side of the gate; forming a third p-doped region in the substrate, the third p-doped region being formed spaced from the first p-doped region by a second spacing; forming an n-doped region in the substrate; connecting the gate with a first node by a first conductive line, wherein the first node is configured to be coupled to a first voltage supply; connecting the third p-doped region with a second node by a second conductive line, wherein the second node is configured to be coupled to the first voltage supply; and connecting the n-doped region with a third node by a third conductive line, wherein the third node is configured to be coupled to a second voltage supply, wherein the first p-doped doped region, the second p-doped doped region, the third p-doped doped region, and the n-doped region are formed within a common, n-doped well region.
 19. The method of claim 18, wherein the gate is formed to have a width equal to the first spacing, and the dielectric layer is formed to have a width equal to the width of the gate.
 20. The method of claim 18, further comprising: forming a p-doped implant region in the substrate, wherein the p-doped implant region is formed connecting the first p-doped region and the second p-doped region. 